The 5-hydroxy-4-thiomethylpyrazole compound obtained by the present invention is useful as an intermediate in the production of pharmaceutical and agricultural chemicals.
As for the process for producing a 4-thiomethylpyrazole compound, a method of reacting a 4-chloromethylpyrazole compound and a sulfur compound is known (see, Patent Document 1).
In order to obtain a 4-chloromethylpyrazole compound used as the raw material of this reaction, for example, after once synthesizing a pyrazole compound having a methyl group at the 4-position by a ring-closing reaction of corresponding β-ketoesters with hydrazines, the methyl group must be converted into a chloromethyl group by chlorination. Furthermore, for obtaining a 4-thiomethylpyrazole compound, this chloromethyl group must be reacted with an organic sulfur compound (see, Patent Document 1). However, this method is not satisfied as the industrial process for producing a 4 -thiomethylpyrazole compound, because the reaction comprises multiple stages and the yield is not high due to difficulty in the selective monohalogenation of the methyl group at the 4-position of pyrazole.
As for the process for producing the 4 -chloromethylpyrazole compound as the raw material in the above-described method, a method of directly chloromethylating a pyrazole compound unsubstituted at the 4-position is also known (see, Non-Patent Document 1). However, this method is problematic and hardly employable as the industrial production method, because the reaction is associated with by-production of a bis(chloromethyl) ether which is a carcinogenic substance.
Furthermore, a reaction of directly thiomethylating a pyrazole compound is not known.
(Patent Document 1) International Patent Publication WO2004/013106
(Non-Patent Document 1) Journal of chemical Society, pp. 1205-1208 (1955)